The monitoring of civil structures and infrastructure has traditionally been done, and is still commonly done, by visual inspection, which can be costly and time consuming. Recent structural failures and the degrading state of the civil infrastructure highlight the importance of monitoring and preserving structural integrity to ensure public safety. The field of structural health monitoring has placed particular emphasis on the non-destructive evaluation of buildings and infrastructure, and a variety of non-destructive testing techniques have been developed, such as pulse-echo, dynamic response, and acoustic emission techniques. For example, acceleration-based measurement techniques are widely used to evaluate a structure's vibration signature.
Strain-based measurement techniques are also widely used. Commonly, strain measurements employ resistive foil gauges or optical fibers. Smart memory alloys and piezoelectric materials can also be employed in strain measurement techniques. Piezoelectric transducers are typically embedded in the structure, and generally fall into three categories: acoustic emission, acoustic-ultrasonic and electromechanical impedance. Electroactive piezoceramics and piezopolymers have been employed in these techniques. Piezoelectric paints that contain piezoelectric particles have also been developed.